This invention relates to a method for controlling a servomechanism by using an adaptive compensating circuitry on the basis of a model reference technique and to an apparatus used for practicing this method.
Servomechanisms of all descriptions are actively used in all industrial fields and further improved efficiency thereof is much desired. The current state of the art has, for example, generated needs for improved response characteristics in the high frequency range in material testing machines and extension shaking tables and for enhanced performance and reliability in robots with complicated mechanisms capable of dealing with objects of various weights.
The ordinary servomechanism consists in a servo loop and resorts to a speed-feedback loop as in a tachometer generator or a lead-lag compensating circuit to ensure the reliability and enhance the performance characteristics of the mechanism. Nevertheless, when a servo-motor is subjected to a large fluctuating load and friction or the characteristics thereof are affected by variation in the power supplied to the servomechanism, it becomes difficult for the servo-system to provide the desired smooth response.
Hydraulic servo and pneumatic servo systems employ a control valve with non-linear kinematic characteristics which affect the performance characteristics of the systems in certain working ranges. Therefore, these systems cannot easily and stably ensure the desired damping coefficient in the speed of response.
In recent years, an adaptive control technique for continuously operating a servo system in an appropriate condition by monitoring its working condition and changing the parameters set in compensating circuits in accordance with the variation of the working condition, has been drawing much interest. This technique, however, requires extremely complicated measures for carrying out the processing of signals by use of an electronic computer, and today's computers do not have high enough operation speeds to follow the speed of response of the servomechanism. Moreover, this technique is complicated and expensive to apply. Thus, the development of a low-cost servomechanism capable of operating at high speed in response to the working condition thereof and to variation in load is strongly desired.